Felix cherished Anne and tried his best to adjust to the new environment where now he was a big brother. So did Lucas as he was basically a parent to Felix first, then Anne.
He even joked how Anne should call him grandpa since Felix, the naive and very innocent young boy had to be taught many things by Lucas who had a lot of experience and was tough with every hardship he had to go through. It's weird how he was better at a lot of things than Felix when he never had anyone to teach him growing up. It's amazing and it just showed Felix how strong Lucas was.
Felix admired him a lot. He listened to Lucas's every advice and always seeked help only from him. It could say Lucas basically raised Felix. Felix himself would not deny that.