From last chapter, we saw that Carla was one of the people Grisha came home to when he gave up on his mission, so he definitely loved her by that point. Theres also his reaction to Carlas death. To me, thats always been the biggest piece of evidence that he really loved Carla (at least before chapter 120).
Did Grisha care about Zeke?
One thing is certain; young Grisha, who still resided in Marley, definitely didnt care much for Zeke. He even says so himself. But this is older Grisha speaking about his past self. Hes criticizing his actions, and speaks with regret.
Does Zeke love Eren?
Zekes affection towards Eren had since developed into a near-obsessive desire to have his sentiments validated by his half-brother to the point where he was willing to postpone the sterilization of the Eldians until Eren agreed with him.
Why did Keith broke Erens belt?
Upon seeing the fire in his eyes, Keith decided to sabotage his balancing test by breaking the fittings of his vertical maneuvering equipment belt, believing that Eren would be torn to ashes if he left the Walls, never knowing Carlas wishes for his life.