(son was appointed trustee of deceased father's trust and personal representative of his estate; son received a $50,000 deathbed transfer from his father which he failed to deposit in the trust account; son also commingled trust property with personal property, and failed to make any distributions to daughter, an income beneficiary under the trust; at the request of the daughter, the trial court removed son from his role as personal representative and trustee; on appeal, the court affirmed, rejecting the son’s argument that the trial court should have used a less intrusive method, such as appointing a special administrator to merely limit son’s role; Neb. Rev. Stat. § 30-3862(b) allowed removal where a trustee “committed a serious breach of trust”; son’s interests irreconcilably conflicted with the interests of the estate and trust, and appointing a special administrator would not have alleviated the problem).