Can beneficiaries to a trust act jointly and severally?

The beneficiaries of a trust are not usually the "actors". Acting jointly or severally generally pertains to entities that perform the same functions such as trustees. A trust can provide that the trustees can act jointly or severally. That means, one trustee can take any action allowed by the provisions of the trust without the consent of the other trustee. You need to add more details regarding how you think "jointly and severally" would apply to beneficiaries.