In the 1750's when Angel was human, his name was Liam. He had a father who worked as a merchant. A mother who there hasn't been too much shown of. A sister who was much younger than he, and he loved her very much. They lived in Galaway Ireland. There was one servant named Ana who Angel had wanted to sleep with, but his father interviened.
Basically before Angel was Vamped he loved to drink, not work--> "My Lady, you will find, that with the exception of an honest day's work there is no challenge I am not prepared to face." It also shows that Angel loved to sleep with as many girls as he could get into the sac.
Angel meets Darla in 1753 after she spotts him in a Bar fight. Darla questiones another woman about him. Then she positioned herself in a direct path to meet him. Their Relationship will be discussed in the Carbon-Dated section. Also we know that while Angel was full fledged Vamp He sired Drusilla, and Pen. No others are known of.
During Angel's Time as Angelus He spent his whole life with Darla. She taught him things, and blew the top off his head. The only time they split up that is know of is in France in 1765. And that was extenuating circumstances. They met back up in Vienna after the ordeal was over. After Angel's soul was returned to him and Darla kicked him out; he wandered about feeding on rats and other animals. He was full of remorse and guilt and really honed in on his brooding skills. Two years later in 1900 Angel finally caught up with Darla. He found her in China in the midst of the Boxer Rebellion. He said she was sloppy. He knew she could never resist a religious war and she had always talked of China. She replied that maybe she had wanted to be found. Angel told her he could be Angelus angain, and that they could have the whirlwind back. It worked. Darla took him back. Angel fed on humans during this time. But Darla was not stupid, nor was she blind. Angel was only hunting evil-doers; Rapists, Murderers; scoundrels and theives. She told him to prove his devotion by feeding on a baby. He could not do that, so he left.
When whistler showed up Angel decided to get cleaned up, and to help the new, young, slayer. Of coarse he and Buffy fell in love. After all, she resembeled Darla in so many ways: young, beautiful, blonde, strong. After they "made love", and he lost his soul he tried to drive her insane. It didn't work. He regained his soul just before taking a trip to hell.
After hell Angel returned to sunnydale for a year, before leaving the hellmouth, and Buffy behind. He then goes to LA, meets the late Doyle, and hires Cordelia and Wesley. Both of them were on BTVS in the previous season. He still broods in LA, but he has many flashbacks with Darla in them. His break up with Buffy is finalized with an exchange of blows, the last time she shows up in LA, on season one. Also Buffy is Boinking Riley almost non-stop so it looks like nothing will ammount romantically between them ever again.
Now Darla is back in Angel's life. Few are happy about this. Darla is hated by Cordelia, and Wesley isn't too fond either. However Angel becomes aware of Lindsay's "schoolboy" crush on Darla. He doesn't like that too much. Angel reminds Lindsay that they were together 150 years. And the only reason that he didn't love her is that he wasn't capable of it then. Well, He sure is now.