In the past I have organized my Dwarves into clans founded by migrant and founder couples in the fortress. When I had my population capped at 50 or less, this was feasible because I only ended up with a dozen or so clans. With the population cap at 200 for testing 31.03, I have so far 45 married couples involving migrants and founders, and 20 migrant females as yet unmarried. Assuming all of the remaining migrant females married, I would have 65 clans. That seems an awful lot for one fortress and, as Tarn commented, an unwieldy number of unique groups to provide for. I am actually ahead of myself in only mentioning the females. Originally I gave equal weights to the males and females. I had not yet resolved the issue of which clan took in the married descendants of the original couples. However, Tarn's comment on religions solved my problem.
I started looking at the religions of the Dwarves in my fortress and discovered that the children of any marriage all follow the religion of their mother. In the case of the one widower who arrived in my fortress with a child, the father and child had the same religion. I could make the assumption that the child's mother also followed that religion, or that the father converted in order to properly raise their child after she died. However, for the purposes of my fortress it is a moot point because that child is male. If the father remarries, which is likely because he now has a lover, it won't matter that his son ends up in the wrong clan because the son will marry out anyway.
Once I resorted the families by religion, still leaving the married couples their family tag for census purposes, I had 10 groups. 10 clans seems much more sensible for one fortress. Furthermore the question of where a pair of married descendants lives is solved. They will move into the clan quarters of the mother. The distribution is interesting and I look forward to seeing how it evolves over time.
Out of 64 adult female Dwarves (46 married, 2 widowed) the following religions are practiced in year 8 of the fortress. There are a total of 44 female children that have not been counted in this list.
Lurit the Spines of Gilding, deity: wealth, mountains, earth, caverns = 20
Savot, deity: courage = 8
Urist Oversieged, deity: fortresses, war = 7
Igest the Fabulous Sweetnesses, deity: art, inspiration = 7
Zuden Searchedwards the Cover of Towers, deity: sacrifice = 6
Limul, deity: jewels = 5
Vir Rainstar, deity: the weather = 4
Esar Glidedgroves, deity: peace = 3
Idor, deity: chaos = 2
Zizcun the Tub of Breads, deity: silence, pregnancy, family, birth, children = 2
Orshar the Naughtiness of Tunnels, deity: the moon, misery = 0