You don't have to have inborn skill to make an excellent builder; I too had a run of kids with no inherited building skill, so I just put them (2 at a time) on a project and watched for a little while to see if any had hidden talent. Some had no knack or desire at all, some made a little progress, but one, a researcher, went nuts, and now, at age 28, he has ~70% on his construction skill bar and 80% on his research bar.