Location(s): Rohan, Gondor
Title(s): King Of Rohan
Dates: III 2905-2980
Parents: Fengel (f)
Siblings: 2 sisters
Spouse: Morwen of Lossarnach
Children: Theoden, Theodwyn, 3 more unnamed daughters
"Thengel. He took no wife until late, but in 2943 he wedded Morwen of Lossarnach in Gondor, though she was seventeen years younger. She bore him three children in Gondor, of whom Théoden, the second, was his only son. When Fengel died the Rohirrim recalled him, and he returned unwillingly. But he proved a good and wise king; though the speech of Gondor was used in his house, and not all men thought that good. Morwen bore him two more daughters in Rohan; and the last, Théodwyn, was the fairest, though she came late (2963), the child of his age. Her brother loved her dearly.
It was soon after Thengel's return that Saruman declared himself Lord of Isengard and began to give trouble to Rohan, encroaching on its borders and supporting its enemies."
Lord of the Rings, Return of the King Appendix A, Section II "The House of Eorl"
Also from Appendix A, Section II, under his father Fengel's listing:
Thengel, his third child and only son, left Rohan when he came to manhood and lived long in Gondor, and won honour in the service of Turgon.
Envinyatar 12.19.02; Loquacious 03.22.03; Thevina Finduilas 10.27.03, 11.6.03