Splitting a tree ?

Does anyone have any advice on how best to share data between different branches of families ?

I am currently linking up with various family members who have done work on their own trees (sensibly enough), but they are obviously primarily interested in the common links that we share and not the really extended elements.

For example, say I have one relative and his relation to me is because both our fathers were brothers. I am interested in research he has done on his fathers lineage (shared with my father, so directly relevant), I am interested in the fact that his father married his mother and they had children, and I am kind of interested in his mothers parents but not a whole lot. I'm really not too pushed about finding details of her siblings and their extended families, etc . . . too much information. So, apart from manually calling back details recorded and re-typing, how do you normally merge two trees without including all sorts of (to me) unrelated information about non-blood relatives ?

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