One for family lawyers regarding custody

[Threeracers]

I could use a little advice regarding custody. I am divorced and have 50/50 custody of my three eight year old children with my ex-wife on a week on week off basis rotating on a Sunday night. The arrangements have worked well for several years.

My exwife is now engaged and her new partner has two kids and my partner has two kids that live with me full time. I am in the process of updating my will and in the course of discussing guardianship etc my partner has asked if this custody arrangement would continue in the event of my death and if my ex-wife’s partner would like it to continue in the event of my ex-wife’s death. I believe it would be good for the kids if they lost either one of us but before I broach this subject, is there any way I can ensure any agreement is adhered to?

My ex-wife was never particularly trustworthy so my concern is that we agree to this continuing but if I died first she would renege on this.

I suspect however that my ex-wife would prefer to have sole custody of my children but do I have any rights to ask that my partner would have continued access to my children in the event of my death? At the moment she spends exactly the same amount of time assuming the “mum” role for my kids as their real mother does but does that give her any rights?

Any advice appreciated.

Many thanks

Mark