YTA. You handled this completely wrong. I agree about the age gap issue, but also your sister has a personal trainer and a chef?!?! Yes, of course it's easier for her to bounce back!!

Along with that, your wife is obviously trying. She just had a baby. She's exercising. She's breastfeeding (you know feeding YOUR child). And you are focused only on her looks?!?! She notices that you aren't interested and rather than support her, you are the asshole husband who can only focus how pregnancy and taking care of two children ages him!!! Your wife carried your child for nine months. Step up, recognize her shaving body for all that it has done to create and nourish your baby. Don't focus on how her lack of looks affects you.

Dang. It took me 18 months to lose the baby weight and I still could lose the last ten. Fifty pounds heavier and my husband made me feel as beautiful as attractive as ever. Yes, do I know he prefers me at a healthy BMI, of course. But he never let that be known and he constantly complimented me and supported me. And made me feel like the only woman in the room.