Are the parents responsible?

My husband and I talked about getting the aunt a car seat for our daughter. She babysits and takes her out or drops her off. He said he likes to give it on the aunts Birthday, that's late summer. I told him, I'd like to get one now, besides it's our responsibility to supply with necessary items that is needed for our daughter if a family members babysits regularly. He said, he doesn't look at it that way, because an immediate family member enjoys the banysitting and thus we aren't required to equip them with extra kids stuff. Well, I'm getting a car seat anyway but what do you guys think?

** thanks for the great input. I've ordered the same car seat we have and will give it to her when it arrives**