A. Ivan and Brynja Stark
B. Scorpio
C. When Anya was ready to have a child and an heir, she sought out Halbjorn as part of the deal their fathers made for control of Stark Inc. Twins weren't that big of a surprise.
D. Ivan: 6'7" red hair and muscled. Brynja - 6'1", red hair and slim.
E.
1. Anya raised both children, but Hal would visit on rare occasions. Both kids saw their aunts Svalin, Asleif, Aridis and Vernique more often than they saw their father. Occasionally Grandma Sif and Grandma Einmyria would visit. They saw Grandpa Thor more than any of the others.
2. They've never been to Asgard. Mom thought it best that they didn't get involved with Asgard issues.
3. Both are stronger and more durable than ordinary humans, but not as strong or as durable as full Asgardians. They'll live longer than normal humans as well.
4. Brynja is the more mischievous of the two and cousin Solver was her favorite targets of pranks.
5. Ivan wanted to play professional football, but couldn't because he was much stronger and much more durable than the normal humans who played. With the help of Grandpa Tony he started a league for mutant/super powered players.