The Aasimar and Tieflings were added with
D&D 3.0 or 3.5.
Ope! turns out they came out in 2.0, in the Planescape Campaign settingThey are both plane-touched, in that these individuals or races have an ancestor who was either a celestial being or a devil. I played January as one in Neverwinter Nights 2.
BG3 has a lot of Tieflings, refugees from a city that was taken to one of the Nine Hells, but eventually escaped. I think that was in the one of the D&D books or other properties. In BG3 that city is back, but the Tieflings wihin were driven out by the other residents because of their devilish ancestry. Basically it is an allegory for racism.
Tieflings are a playable race in BG3, and one of the most memorable companions - Karlach - is a Tiefling. But Aasmar are not playable. Maybe they are saving that for a DLC? The one NPC in the game is not your typical Aasimar. She is the daughter of Selune, goddess of the moon. So she's really more of a demigod than the standard Aasimar in D&D, who just have a little bit of such blood somewhere far back in the blood line.