(For context, this answer is taken and adapted from a private conversation. I know what neb090 is trying to say from previous messages.)
Here are some positive sentences using the phrase 'either of them':
- "I can lend you either of them, whichever you prefer."
- "You can choose either of them; both options are equally good."
- "She could invite either of them to the event, but she hasn't decided yet."
- "I'll accept either of them as payment for the services rendered."
- "You're welcome to borrow either of them from the shelf."
- "I don't have a preference; you can choose either of them."
As you can hopefully see from these examples, the phrase 'either of them' in each case means something like '
it doesn't matter which'.
If you say
Johnny has two bikes, it doesn't matter which was from his dad, I really hope you can see how that is not what you mean and in fact makes no sense. What you mean is that of the two bikes, one was from his dad and one wasn't.