Should I spend alone time with 1 twin?

Based on my twins, my answer is NO! I have tried since the beginning to take just one of the boys to run errands, go to Wal-mart, go grocery shopping, etc. The whole time we are out and about, he is asking me, 'what do you think my brother is doing?' The twin that is with me is feeling as though he is missing something else that is going on. The twin that is left with the grandparents or at his dad's house, feels the same. The entire moment that is meant for bonding and pleasure between a mother and her child, turns into a competition of what one got to do without the other and what did they each miss! When their conversations take place concerning the other's activities in the absence of the other twin, it turns into a fight, someone starts pouting, then the all-to-familiar name-calling begins. I have found it is so much simpler to just drag both of them everywhere I go and allow them to experience everything together at the same time.