Mom is a state of mind.
I've seen a lot of interspecies friendship videos, so I know that sometimes they can be a bit dubious, like the camera person just happened to capture a moment when two animals were near each other. Not this one! This orangutan is flat-out loving these tiger cubs, and has learned how to give them milk from a bottle after watching the human handlers do it. Also, the petting! The playing! The cuddling! This video reeks with the stench of what is inarguably love, even though neither the cubs, the orangutan, or any of us watching share the same chromosomes.
OK, ok, ok. There is one caveat to this orangutan serving as a stand-in for adoptive moms, and that's his dick. However, he's a young orangutan, and "Younger males do not have [cheek pads that produce long, loud mating calls] and resemble adult females." Also, it's 2015 so why don't you get off this orangutan's dick and admit he's a good mom?