Reading up on molecular biology and its impact on archaeologly I came across this article which confirms findings from a female burial that came up in connection with the battle of the Tollense crossing:
https://www.pnas.org/content/114/38/10083
Basically, this is proof that people found their wives outside of their own communities. What is surprising is that these wives often traveled more than hundred kilometers (or miles) to their new homes.
What is strange is that there is hardly any evidence for their offspring in the area investigated (the Lech valley upriver of Augsburg).
The model of Heortling exogamy for Sartar might be rather hide-bound compared to these early Europeans. The Sartar dynasty might be one of the few bloodlines with similar variety in their wives, including Grazer, Old Tarsh, Telmori and an attempt at Esrolian ancestry for their partners.
Tooth chemistry suggests that these women were well over 16 years old when joining the population on the Lech. Given a generally shorter life-span in those times, I wonder whether they left some children at their old homes before making the trek to new hearths. If these people practiced something like serial monogamy (on the side of the wives, no idea about the males), creating their family trees will easily become a wild web across communities.
The Ernalsulva marriage in Sartar: Kingdom of Heroes suggests that at least Gloranthan earth priestesses undergo such serial marriages, joining more than one marriage partner's clan throughout their lives, although unlike these women their male offspring remains with the paternal clan. The females will spread on, of course. When checking the possible family network of a 90 year old priestess of Asrelia, I came to the conclusion that her female lineage offspring would realistically be spread across several tribes, as priestesshood tends to run in families given the special educational benefits of growing up in a priestess' household.
I have a slight beef with the sample characters of RQG in that there are two females born into their paternal clan and still being active members, although in both cases they are valid exceptions - Vasana has taken the Vingan role, which tends to remain in the paternal clan, and Yanioth is a priestess of the Clearwine Earth temple, which is almost a matrilocal clan of its own. They do set a precedence which will mislead players with less familiarity with Orlanthi marriage customs to assume that most females stick with their birth clans. Luckily the Red Cow HQG books set this straight, presenting some female politics on the sidelines of the Eleven Lights campaign.