How to 'interconnect' two trees


I’m wondering, is there somewhere a guideline how to interconnect two Family trees with each other?

Tree 1: Miller, Tree2 : Johnson

Problem: a member of family 1 (John Miller) is marrying a member of Family 2 (Cindy Johnson)

Are these trees automatically interconnected when I enter the marriage between those two people?

PS. Cindy Johnson is the Daughter of my wife from her 1st marriage and I want to build up the tree for that family too.

Any feedback is much appreciated.

Environment: Linux Mint v20.3, Gramps v 5.1.2

It depends on what you mean behind the “interconnected” word.

Gramps describes persons. The record contains everything needed to identify a person: name(s), personal events, citations, e.a.

These persons are “connected” through family records. A family has a father and a mother (in the traditional model, adapt for other contemporaneous models). This makes the link between the “spouses” (note that relationships other than marriage are possible; the goal is to document the lives of people, not to moralize). A family can host children. Enumerating them makes the link with the next generation.

With persons and families you build a graph. on any path you alternate between person and family.

So, this is not the marriage event which “interconnects” trees because an event is only a “comment” or “proof” for a record. You must create a “family” into which you designate the “spouses” and you add there children.

Through the family records, queries like “find all ancestors” will work as you expect.

The best is to use One database for all your trees.
There is no way to connect people between different databases.


We ought to confirm a few assumptions…

Are there 2 Trees because there were Genealogists in each family who created a Tree? And now you want to consolidate the research?

That would be a complex operation even if both genealogists were using Gramps and you could do a lossless import of the backup from one Tree into the other. If both were NOT using Gramps, it is even uglier because that requires falling back to a lossy transfer format like GEDCOM.

It is comparatively easy to import a file and graft the branches together with a single Tree member joining as spouse/partner in a Family with a member of the other Tree. But fully merging the overlapping duplication of Places, Sources, Citations, People, Families & Events is a hugely complex undertaking. And, if both families were residents of the same region, there is certainly going to be a lot of overlap.

So we don’t go off on tangents, maybe you can clarify how you came to have two databases (Trees)?

The scenario described by ‘emyoulation’ matches the situation very precise.
As you call it two Genealogists created two trees. Now I understand… one tree means one database, two trees two db’s.
To be more precise, family-1 has a family tree with about 4 generations. Family-2 has a family history over seven generations.
A descendant (of family-1) in the 2nd generation is married to a descendant (of family-2) in the 4th generation.
Otherwise there are no overlap between those two trees.
I would like to manage both trees in one stream and create reports just from a different starting point in each family hierarchy .
Does that make sense to handle it in this way?
What reason would speak against it?

If you can get a GEDCOM file for each of these, you can import them into a single database tree in GRAMPS. Make the family connection and you have one big tree. As previously stated, you will have to cleanup/merge some items such as Place names. If you do this, add the Latitude and Longitude to the records and then the mapping feature works too.

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Thanks for the advice. I have to ‘digest’ this before making a decision.
Would be nice to hear some opinions what the better way would be; keep them in separate trees or have them in one big one.

Just another point. You can only do this once or all your work will be lost. You can’t re-merge the other trees into the database later. Any updates in either tree that happen, you will have to do manually to your combined tree.

Absolutely merge the 2 Trees by importing them into a fresh blank tree. (Until you have confirmed everything transferred properly, you’ll want to leave the originals intact. Because this gives you the flexibility to revert and try a different approach.) The first import will your foundation.

Before doing the 1st import, check your Preferences. You’ll want to make certain that the first two checkboxes in the General tab are selected. You want to annotate each of the imports with a Tag and reference its Source. This makes it easy to still filter the fully merged tree later into those original pieces.

Unless merging your Tree will create an unmanageable number of duplicates or a wildfire hazard, a merged tree is preferred. (My overgrown forest of a tree is nearing 50 thousand people and is becoming less responsive on my older laptop with a mechanical HDD. It would be much better running from an Solid-State Drive.) In fact, the standard recommendation is to ALWAYS work with a single comprehensive tree.


Definitely all branches of the tree in one database. One branch will be the Miller family. The second branch will be the Johnsons. But if and when the next generation is added, their branch will be the Miller-Johnson family.

Maintaining just one database will also make it easier to maintain the Place and Source records…

I personally currently have two trees, because I got them that way from other people. I have made so only one single person is in both trees currently, as far as I have seen they havent had anything else in common yet.

I do plan on merging them myself, but that is after I have finished going over data already there in both trees and improving them. Currently I have only been doing it on one of them.