futo is tojiko's mom/stepmom isn't necessarily true because:
1) soga no tojiko will not talk is not a suitable source of historical fact
2) names like futshime or futohime weren't exactly rare in the mononobe clan(futo could have been for instance the wife of emperor sushun)
3) unlike miko and okina, futo and tojiko aren't officially 1:1 with any historical figure and zun pretty much states this