They are joint tenants on the property and he is free to come and go as he likes but he needs to be careful because in circumstances like this, ex partners are adept at alleging domestic violence et cetera et cetera to get their own way.
A couple of solicitors and barristers that I know, and I agree with them, estimate that at least 50% of the allegations of domestic violence, which are made when a couple split up, are without merit/spurious/Lies. So be careful.
Although he is entitled to come and go as he likes, she is also entitled to have guests in the property although if she goes to the shops or out, he is entitled to ask the guests to leave and she can invite the guests back in the game when she returns.
Legally, straightforward but practically, a nightmare.
The local authority will not rehome him unless he is evicted because they would see him as having made himself homeless if he leaves voluntarily.
I can understand why your son is upset at having this person around the children and there is no reason why he could not make an emergency application to court for a Child arrangement order which, amongst other things would exclude the new partner from being near the children.
Fortunately, there is a lot of information on the Internet about Child Arrangement orders and the government have actually produced a guide on the subject which is here.
The different types of Child Arrangement order are:
1 A Contact Order which specifies when parent sees a child,
2 A Residence Order to determine who the child lives with,
3 A Prohibited Steps Order to prevent a parent doing something with the child such as moving away either in this country miles away or taking the child to another country. Particularly relevant if there is a chance that the parent would go to another country and never return. The parent wishing to prevent the move would have to convince the court why it’s not in the best interest of the child to move. Friends, support, school et cetera et cetera all taken into account.
A Prohibited Steps Order is to prevent child Abduction and it’s one of the few areas of law for which legal aid is sometimes still available. It’s often therefore worth seeing a solicitor.
4 A Specific Issue Order to allow a parent to do something specific with the child such as moving away to another part of the country or indeed to another country. . The parent wishing to move would have to prove why it’s not in the best interest of the child to move.. Friends, support, school et cetera et cetera all taken into account. It would also encompass things such as changing school if the parents cannot agree, changing the child's name, and anything other specific.
The courts will not get involved in a Contact or Residence order unless the couple have been to mediation first. So the couple would have to try mediation even if it subsequently fails and the matter proceeds to court.
There is no reason why he could not get an order within a couple of days because clearly there is some urgency here because of the nature of the individual.
It would be worthwhile speaking to a few solicitors to see whether this could be dealt with on legal aid.
You might need to ring round an awful lot of solicitors but you can search by postcode and specialism on the Law Society website www.lawsociety.org.uk find a solicitor link which is at the top left hand corner of the page.
Thank you for letting me assist you with your legal question. I am glad that I was able to help.
I am not certain whether that answers the question for you or not, but I am happy to answer any specific points arising from this.
It will be my pleasure to help you again either further with this or any future questions you have