I believe Thomas and Nicholas would be very fun to plot with! I'm still working out Mads' background, but we can absolutely hash out how Thomas and Mads know each other.
As for his sister, she's the daughter of a helot his father was particularly fond of. If you want to give her siblings, I am okay with that, she'd just be the most important. Mads takes very good care of her and she can do essentially whatever she wants. The one caveat is that she cannot have is a lover because it makes him jealous. Whether or not their relationship is sexual, I was going to let the other person decide, because I am fine with it either way. If you're still interested, I can set up a custom and we can discuss it further!