Is this normal for a 7 year old

So tonight I was putting the kids to bed.

And we've noticed our 7 year old is not empathic at all.

When sad things happen, like when our dog died, he laughed because everyone was sad.

He sleeps together with his 10 year old brother, and his brother was absolutely devestated about his friend who was like a brother to him ignored him because he started out hanging out with another of his "friends" who called him a "something cancer something" he didn't fully remember because it happened over a week ago but he hadn't told anyone (He has a lot of trouble voicing his negative feelings as he has some kind of dissability, I don't know what it's called in english though, I'm really thankfull of him being able to open up to me ❤)

So he was telling me all crying and devestated and barely getting it out...

Meanwhile his 7 yo brother is making fun of him crying.

I told him to knock it off, so then he tried doing it behind my back

In the end I told him.. and I may have crossed a line there (because he's only 7) but I didn't know how to propperly react to it... that it was very very insensitive of him to make fun of someone that was allready feeling so sad, and that it broke my heart (I cried when I said that too, I really felt those words were truth but maybe a bit harsh for a 7 yo), and I said goodnight without kissing him goodnight, which I usually do.

I didn't feel like my words made any difference though he just was angry because he didn't get what he wanted (goodnightkiss)

I'm just wondring if this insensitiveness for (other people's) feelings is normal for a boy his age maybe?

** (extra info, I won't be able to update because it's a poll)

I'm a step parent so really raising him hasn't been my job, I do my best with the tools I have but it's still limited. (I do have a good amount of authority because I take care of them for 70% on my own in the time they're with us.. can't do that without any authority)

Earlier today I had a talk with said 7yo and he told me he didn't at all understand why he can't just do as he pleases anytime because his mom allows him to.

He gets food when he gets home from school and is allowed to eat anytime, leave the table and run around with food, he can choose to not eat his food but eat candy instead. He can choose what's on tv and has his own tablet and has unlimited amount of access on there and he doesn't have to brush his teeth because nobody checks and he can take and eat candy and ice cream whenever he wants to. So anyways, he blames us for not doing thesame.

So with that in mind, I can imagine his mom's first priority is not on raising her kid so I don't know if it's age bound or just the lack of raising or is it personal or maybe genetic? (According to my husband his ex isn't empathic either, I've heard some examples of that but it's all secondhand, because to me she acts like a childish bitch.. anyways some women feel justified doing that to their ex's new partner so I'm taking that as childish but sortof acceptable? The only firsthand proof I've seen about it is how she talks about her kids like they're failures and all hopes are on the 7yo now because the other 2 are stupid fucks..the kids were sitting right there with us, she was talking to my husband, made both our blood boil but we were at a school event so we ignored that trying to not make a scene)