Overly critical of me but kids can do no wrong

I am childless with 4 stepkids. I am not sure if this is unique to step parents or if my SO is just a jerk. But what I am wondering is if you guys are experiencing that same thing? I don't know if it comes from guilt of the divorce but my step children literally are perfect to my SO. He will twist and turn anything they do bad into it not being their fault. He holds them accountable for nothing. As you can imagine it makes them pretty insufferable to be around. But then when it comes to me he can find the smallest fault. He nit picks everything I do. I asked him this morning why he's so critical of me and he said I just can't take criticism. Just for a small business example this morning and what got me thinking about this: I said hey can you get your son to sweep his hallway. I know you asked him the last two days in a row and he still hasn't done it. His immediate response was he didn't hear me ask. I said hey did, he acknowledged you and said okay when you asked him yesterday. He mumbled under his breath again, he didn't hear me. Then a couple mins later walked by the kitchen table where I had some lemon wedges I squeezed into my water sitting by my water cup and he said are you ever going to throw these away or are they going to sit here all day? lam not a person that leaves trash around and I. No world would they have sat there all day but he still said that. It makes me feel unloved, especially when he gives so much grace to his kids.