Can he travel to a kaafir country for the sake of upholding family ties?

It is not permissible to travel to a kaafir country except for a valid reason such as studying to acquire knowledge or skills that are not available in a Muslim country, or for medical treatment. But the traveller should have sufficient religious commitment to protect him from temptation and sufficient knowledge to protect him from doubts. Keeping in touch with relatives and upholding the ties of kinship can be achieved through lesser means; you can call them by phone, or correspond with them in any fashion, or send greetings and gifts, and so on. A person should not expose himself to the risks of travelling to a kaafir country and committing sin for the sake of something that may be achieved through other means. And Allaah knows best.