Darkness Unbound question

Oh my god this is a easy one this book is a spin off form Keri's other series The Riley Jenson Guardian Series. It is an excellent series check it out if you have time it is one of my favorites. But any way Riley and Rhoan are twins, Rhoan and Liander are lovers, Riley and Quinn are lovers. Riley could not have kids so Liander's sister carried the kids for her and Liander. Does that make since or help?