child custody issue

[Frazzled2207]

DBil has a ds (my dn) from a previous relationship. He is 13, they split up 6/7 years ago, never married.
Since then they have lived in same town less than a mile apart and custody has been 50/50 (agreed between them so not formal). This has been broadly satisfactory for all. Now his xp has started a new rel. with a man in a city 200 miles away, and is expecting their baby next month. She is talking about moving to her dp's city and taking dn with her.
My dBil is furious and will take it to a family court if necessary to make sure this doesn't happen (obviously can't stop her from moving but she is not to take dn with her). He will fight for full custody if necessary. This is causing much angst in the family, not least for for dn, who does not want to move 200 miles away or be separated from either parent.
We're convinced it's a no- brainer and that family court will rule in dbil's favour, are we right?
Factors to be aware of

1. Dn is happy with current status quo and does not want to move
2. He is settled in yr 7 at school with friends. This is private school that dbil pays for.
3. He currently lives close to three surviving grandparents, cousins and other family (on both sides) who he sees a lot and has a good relationship with.
4. DBil has good, well-paid job with flexitime which helps a lot with childcare. He has contributed close to 100% financially for his upbringing.
5. Xp has never had anything other than very part time job, she survives on benefits and handouts from her parents and Bil (because he wants to be sure his son is living in reasonable conditions when not with him).
6. New stepdad has a job and would be supporting xp, dn and new baby. He has tried to move to closer to where xp, dn and Bil currently live but apparently given his job situation this is no longer possible
7. New stepdad is a decent guy according to dn but they don't know each other well at all. Xp got pregnant soon after they met, they have never lived together so uprooting ds would be risky at best as there's no telling that the relationship would last.

We can't see that any family court would send dn away from his father in these circs.
Do we need to worry and any specific advice?

Thanks!

[FTFOAFOSM]

It's not really about whether they would 'send' dn away, or whether they would 'allow' her - if it's within the country she would have the right to move, BUT she does have a duty to somehow make contact work - whether that's DN seeing his dad during the holidays, and her having him term time, or something else, maybe where she brings him back for contact every other weekend? It's quite complicated, and while they've had 50/50, if she's been the primary carer of DN and he'd have a stable family unit, there would not really be much to it, other than the change that the move would bring. As DN is in Yr 7, his wishes and feelings would come into it, but DBIL paying maintenance/school fees wouldn't.
There are some really useful books out there on the subject, like 'Family Court without a lawyer' for one. It stresses just how court is the absolute last resort and DBiL would HAVE to try mediation first.

[Frazzled2207]

Thanks both. Fortunately I don't think she would just leave at this point, and even if she did I don't think her son would go. Hopefully she'll realise before it all gets too nasty that she has to stay, or let him live with BiL.

[Pisssssedofff]

Erm she does not have to stay or let him live with BIL .... That's what he wants the court may give her permission to go.

[NRDAD]

Im going thru something similer just now but no new baby on the way. In my opinion. She is the one making the choice to move so the sacrifices should not be forced on her son and ex she should be making them but im sure there will be plenty that disagree.