5yo hitting and biting when he gets upset

Hi,

I'm not even sure how to begin - my nephew is 5 years old, and I have long suspected him to have some form of neurodivergence. Since I'm (rather freshly) diagnosed with ADHD and possible autism, this suspicion has grown stronger, seeing that neurodivergence is inherited. My brother and SIL are wonderful parents, they are open to the general concept of neurodivergence (much unlike my own parents), but I haven't had the guts to tell them what exactly I think. Firstly, as a professional, it's simply not my place - we leave that to pediatricians. Secondly, though I know they are both open-minded, I'm afraid it might in some form harm our relationship, because it's a big step admitting that your child is "different", and they have a lot going on in general.

He's generally a lovely kid, thrives in school, loves trains and is quite creative; his little brother is a livelier 3yo who likes running around a lot and adores his big brother. There's a baby on the way and due in about 2 months. They get along as well as brothers do. But since lately, the older one has started hitting and biting when he gets upset. I witnessed it just today, and to me, it reads as some form of neurodivergent overstimulation. It usually results in shouting, crying and the parents intervening, as I'm told. He has bitten his mom and punched her in the stomach, and since she is visibly pregnant, I find that quite concerning. (Though I do realise that some of his behaviour might be related to the fact that there's a baby on the way.)

I work with toddlers and have no children of my own, so I'm not too familiar with how normal this behaviour actually is. "My" toddlers I monitor closer than you would two older children, and I redirect their behaviours towards more acceptable ones. With my nephews, I don't, because I can't (they live about 300miles away) and frankly, that's not my job.

So, I guess I have two questions:

- How normal is a biting and hitting 5yo after what I have described?

- Is there a way to respectfully tell his parents that they should pursue a diagnosis?

Thank you for reading all this. Any and all kind advice is appreciated!