髪形だけ父さんに似せてもお前は跡取りになれない
Real son says that to adopted son.
だけ + ~ても confuses me. Does だけ replace は/が or を? If は/が, it would be "Even if only your hairstyle makes you look like dad [...]"/"Even if your hairstyle is enough to make you look like dad [...]" and it would make sense, but if を, it would be "Even if you make only your hairstyle look like dad (dad's hairstyle) [...]" and "only" would make it weird, given the rest of the sentence.