name change

[west ham fan]

Hi a few weeks ago I asked a question in the law topic about entitled { same rights}, well this is on the same situation, a quick up date for those that don't know, my son has parted from his girfriend of 10 yrs they are breaking up every 6months atleast ,the problem is they have 2 little boys 9yr and almost 8yr,she is now allowing my son to see them of a Saturday afternoon, she has now told my son she is going to change their surname to hers because she is fed up with having to sign any corrrespondence in conjunction with the boys in her name and in brackets write mother.My question is can she change their name without my sons consent. He is in the process of seeking advice about obtaining a parental responsibilty order. thankyou