Mr. Planché reviewed existing sources and tried to improve upon the accuracy of what he found; there is more recent research arguing many of the questions that come up in these texts, and you should be sure to search for current views rather than take these texts as fact; this is but a starting point for those trying to trace Norman ancestors. Check Medieval English families on the internet from Chris Phillips for more pages on these names. There's the Gen-Medieval discussion list, and the research of COEL (Continental Origins of English Landowners).

Planché wrote, "Next to the brothers of the Conqueror I have selected for notice four of his companions allied to him by marriage, firstly, because an account of them forms a portion of his family history, and secondly, because recent researches enable us to rectify some serious errors which have been repeated for centuries by French as well as English writers, until they have become as it were stereotyped in our national annals."
Planché wrote, "My object in selecting the above three companions of the Conqueror for the subject of this chapter is to vindicate them from an accusation brought against them by an anonymous writer, who, though he may have been contemporaneous, I consider very unworthy the trust that has recently been placed in him. I shall, however, reserve my defence for the close of each memoir, after I have made my readers better acquainted with the personages themselves."