6 month Golden Retriever Jumping at people

I have a 6 month golden who has literally just jumped at a man on our walk and i’m so embarrassed. he’s fairly well trained but this is such a teething spot for us.

he jumps up when he wants attention and i’ve been training him to sit when he wants something at home but when my partners parents come in he jumps at them and they reward him with attention and even bring their own treats… i’ve told them to stop but they keep doing it and i don’t know how to get around this. the other day his dad was holding his arms as he stood up and was saying “good boy” 🫠 they even say it’s okay and they don’t mind but i keep telling them that i don’t want him to jump on a child or anyone else

it’s now happening on walks where he sees a dog or person walking past and will sometimes just stop and stare at them but other times he will literally jump up at them. i just don’t know how to stop this behaviour because it can be so random at times and i feel like home training isn’t helping him stop.