Love / Age difference in Dating a Polish - Is it ok for Man 27years to date Polish Lady 39years? [19]

Hi Everyone, my brother is 27, he lives in London and want's to date a 39 year old Polish Lady. The woman likes him and he likes her, but I don't think that is right for him. So we are trying to discourage them. But at the same time, we don't want to stop a relationship that might be successful. Please what is your advice on this?