You really do need to obtain specific legal advice on this matter, but generally speaking, your partner and his wife are free to agree whatever terms they wish with regard to the distribution of marital assets. The courts will only become involved in you ask them to. However, if the courts do become involved, their first consideration will be the welfare of any children of the family under the age of 18 and it is highly unlikely a court would force your partner's wife to sell the home while the children are under 18, especially if it would mean the wife and children's accommodation needs being placed in the hand of the state. (The courts can order that the wife sells the home once the youngest child reaches 18, but as this is 12 years away this is not much use to you.)