ID orphan orchids?
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Your two orphan plants are not brothers or sisters.
The one with the large dark green leaves as you suspected is an orchid. A Phalaenopsis specifically. This plant will bloom approximately every year on a stem that originates at a leaf base. The flowers will remain healthy and attractive for over a month and sometimes even longer. As you suspected there is plenty of information on the care of this plant on the web so I won’t go into that. Two cautions however: 1) never let water remain in the intersection of the leaves and the stem or in the top part of the plant where the top leaves form sort of a cup and 2) do not water with salt treated soft water.
The other plant is a succulent of the family Graptopetalum. There is also an abundance of web information on the care of these plants and since I never have raised one I don’t have any special cautions.
Good luck with the plants
Since it sounds like they were both adopted by you that probably means that they are step brothers and sisters. Enjoy them but don’t spoil them. Tony