Aye. Gawain, Agravain, and Gaheris are their brothers. I think a good amount of images on this site are missing familial relation tags, mainly these characters. Also for example, if Gawain, Mordred, and Artoria were all in one picture, wouldn't it have the following tags: Siblings, Brother & Sister, Aunt & Nephew? Since Mordred is Artoria's only child, I think that makes her the aunt of Morgan's other children?