I would not venture to say what you should do in your specific family situation.

However, I will share with you how I handle such things in my own family, fwiw.

My approach within my family is to speak with whomever I want to if they are willing to speak with me. I do my best to establish friendly personal relationships with everyone.

With regard to your cousins, in my family I would want to say something like "I wish that we could see each other more." or "I always enjoyed speaking with you in years past." I would want to speak about school, work, etc., aiming to have what I take to be a normal conversation.