Your engagement means you are involved with his family, and if you find the questions weird maybe it is their way of asking you to think twice about marrying this guy? In love you love everything about your partner, and if they are a baldy then what is there not to love? You love him and all of his imperfections, but they are the same imperfections that make him so lovely. You love the whole.
It could be light hearted, it could be deadly serious. Are you two really compatable?
Unfortunately you marry into some extended family of cranks, weirdo's, jokers etc etc
Only you know, if you fast forward and envisage life every day being with this person whether you have made the right choice. If spending every holiday with his family creeps you out you might be better cutting your losses and finding a new partner? If your love for each other is strong enough you may have to discuss how you cope with those irritating relatives. But maybe that is what your Brother in Law if trying to get you to do? Does he see something amiss with your relationship that you don't see? Be honest, look at the cold hard facts. Do you want to wake up next to 'that' face for the next 50 to 70 years? Will you still love him when his head is in the toilet and his smelly underpants and socks are left lying on the floor festering away? Have a happy life. Life is too short not to.