@Twenty4carats I think it's more that he was "free" to do as he pleased and didn't have to worry about leaving anyone behind should something happen to him. Now that he has family, he has someone to look after(meaning he can't just go anywhere anymore) and should he perish then Shiori will be alone like she was before. Sure, she has friends and a few people she can depend on now, but with the ways things are he is the one she trusts and depends on the most. Iirc, he's the one that ensures that no scumbags come by and try to take advantage of her like the first party she was in did. If he's gone, then there is a high possibility someone will take his position at the guild who might pressure her into forming a party again with people that might or might not hurt her.
...and yes, he might have got brother -zoned. Could go either way.