Feanor had a complicated relationship with Indis’ children, but I do firmly believe it was that: complicated. Not cut-and-dry antagonism and opposition. Why? Because I think the story characterizes Feanor as someone to whom family is extremely important. I think in other circumstances (ie: if Miriel had been the one birthing his siblings), he might have been delighted to be a big brother.
Feanor is obsessed with his mother’s legacy, not just as it pertains to his own legitimacy, but for her sake; his grief over her loss is arguably a catalyst for much of his behavior. He adores his father ( “...his father was dearer to him than the Light of Valinor or the peerless works of his hands; and who among sons, of Elves or of Men, have held their fathers of greater worth?” Of the Flight of the Noldor; The Silmarillion). He married his wife in defiance of the expectations of the Noldor and hers was some of the only counsel he would take. He had seven children among a people who conceive only by choice, and named them all after Finwe.
Clearly family is really important to Feanor.
Therefore I do believe that despite his negative associations with his half-siblings, there was affection there. There were times they got along and he did things with/for them and maybe even times he would admit to enjoying having them around, but he could never get over his insecurity over what they represented (Indis’ attempted usurpation of his and his mother’s positions, in his mind) or his resentment about his father’s remarriage to have a more positive, less complicated relationship with them.