There are six beneficiaries in my mother's will. Can some of the beneficiary's bequeath their inheritance to others?

In general, the answer is that a beneficiary under a Will can generally get the benefits he would receive to another person. The issue, however, is exactly how that happens, and what, if any, tax effects there may be. I would like to note, however, that "bequeath" is NOT the word you want here: to bequeath anything to another person, you have to write a Will that provides for the bequest and then die. I don't think that's what you want to do here. There are two main ways that assets can be distribute to your brother instead of the other beneficiaries who want their shares to go to him: either the beneficiaries may be able to disclaim their benefits, in which case they may pass to the intended brother under the Will's terms, or the beneficiaries who want their shares to benefit the brother can accept them, and then make gifts to the brother. Disclaimers, if possible, would be the most generally desirable option. A proper disclaimer is simply a refusal to accept a benefit. A disclaimer must meet very specific rules to be a qualified disclaimer, but if the disclaimer complies with all the rules, the person disclaiming is not going to be found to make a gift to the person who ends up with the disclaimed benefit. Disclaimers are not always possible: the Will's terms may not direct disclaimed assets in the desired manner, it may be too long since your mother's death (9 months is the deadline), or a beneficiary may be on needs-tested benefits and therefore unable to disclaim without creating problems for himself. Find a good attorney and have the attorney review the situation and the Will, determine whether a disclaimer is possible, and help prepare needed documents if so. If disclaimers will not work, then there are always gifts. Again, legal advice for the proposed gift-makers is a good idea.