I've got a feeling that I'm going to get told off here by asking such a stupid question. 
But I'm feeling very much uncertain what to do with DS1.
He's 9 years old and a smart loving person. But he's been held back by lots of issues which are just within the borderline so wouldn't been taken seriously by the system (tried to talk with school before SENCO dismissed our concern even though several of his previous/current teachers implied he falls "just" within the normal range).
He's displaying lots of ADHD symptoms but not as bad as to be seen as disruptive to the class. But he's suffering at a personal level without even realising. He still has no sense of personal space. In the earlier years, he'd roar right in front of other children's face. He still frequently cut in when other people are talking/engaging in activities so as to drop a line of silly jokes. Very off putting for other people. He has hard time to engage in a back-and-forth conversation with his peers, as he always turns the entire focus on his own experience and goes on about it. He seems to be unable to ask any meaningful question of other people's life, as he's just lack of awareness of what's going on around him. He struggles with articulate/elaborate his thoughts and always leaves out key details to make himself understood. All in all, he falls behind his peers in term of speech and maturity. He only has had one close friend since reception year and that child is playing less and less with him now. I really feel sad for him.
Only after I have had DS2 who's 2, I realised how poorly I had fulfilled DS1's sensory needs in the earlier days - simply because I didn't know anything and worked full-time with little energy/time left to know better. (probably a bit stubborn too...)
I've always thought he's lack of sensory input. That explains lots of his behaviour like play fighting, constant fidgets and etc. He also had lots of balancing issues when he was little. I remember he was getting tripped over frequently until around his 4th birthday. We've been holding back to teach him using shoe laces up to now, as it's beyond his motor skill at this moment. We've done Retained Reflex Therapy for over 2 years before the pandemic. I can't honestly tell if it made any substantial difference.
Lately, I realised DS2 doesn't like swings and resist seesaws or anything which rocks/swings him. This leads me to do some more research about the vestibular sensory. It brought back the kind of hope I put on the retained reflex. I start thinking if helping to stimulate more of his vestibular sensory would make any changes.
It's rather naive and too much of an attempt to simplify a complex problem. I know...but DH is very reluctant to go down the route of diagnose DS1 on ADHD. I just feel want to do something to help him at a manageable level...
Anyone who has experience with stimulating vestibular sensory to improve behaviour? I'd love to hear from any OT if my thoughts make any sense at all...