a) SHE is the partner of his sister. He's totally supportive of his sister and her being a lesbian but he knows her lover is bi-sexual and he happens to fall for her...
b)She is the new teacher at the local school. Probably an all-girls school. And she discovers a side she didn't know she had........
c)Brother A and his wife had tried to have a baby for years but it never worked out. Now his brother B offered to have his wife help them out to carry the baby...but brother A insist on creating the new life the natural way....