Methods of joining members, forming molded portions with members, securing inserts with members, and joined members, such as for a frame or a frame for a fenestration unit, formed thereby, are disclosed. One embodiment of the method includes placing a first member with a first cavity in a joining position, placing a second member proximate the first cavity of the first member in the joining position, injecting a resin into the first cavity, allowing the resin to solidify at least partially to join the first member and second member to form a joined member, and removing the joined member from the joining position. Optionally, the joined member can be formed in a fixture, can include molded portions formed by the resin, and/or can include inserts held in place by the resin. Further, members without cavities can form a cavity that can receive the resin.