Hello and thanks for your question.
There are two separate issues - how much time can you have with Adam, even if he doesn't come to live with you, and can he come to live with you.
In any dispute concerning a child, the court's decision will be based on what is best for that particular child, rather than on who shouts loudest.
The court has to consider all the factors in the welfare checklist in the Chdilren Act 1989, which does include the wishes and feelings of the child concerned, taking into account the child's age. The older a child is, the more seriously his or her vews will be considered by the court. But Adam at 11 is still a bit too young for his views to have much weight in a court case. It tends to be children of 12,13,14 and older whose views carry a lot of weight. But Adam's views would still be taken into account - just not to the extent of deciding the case.
I predict that Adam's views about his contact with you would influence the court to order that he should have regular contact with you, more generous than you are currently getting, but probably not as much as you used to get in the past ie not staying for weeks at a time. Any contact arrangement has to be practicable as well - so the court might or might not not say that you have to have the other children at the same time - it would depend what was workable for everyone concerned.
However, I think it is highly unlikely that you will get a court order to say that Adam is to live with you from now on. The court has to consider his relationship with his siblings as well as with his mother and her new partner. It's rare for a court to order that siblings should be split up, and it's unlikely that Adam would be moved away from his mother unless there was very strong reasons indeed, and what you say about the mother's new partner would not be enough.
Where there's a dispute about where a child should live or how much contact they should have with someone, any of the people concerned can apply to court for a child arrangements order, which will set out in detail what is to happen.
To apply for this order, you need form C100, here:
Grandparents aso need to apply to the court for permission first, and that is on form C2, here:
The fanily court now requires that the parties attempt mediation first, before it will consider an application to court. Here's where to find a liocal family mediator:
I think you would also benefit from some face-to-face legal advice. Here's where to find a specialist family law solicitor:
I hope this helps and I wish you the best of luck.
Thanks and best wishes...