Isaak was glad to know someone who could also see the creatures, when he first saw them and didn't really know anyone else who could, he had worried about his mental state and was scared that he might have been seeing things. but he did eventually learn about the Thestrals after doing some research about them.

"Yeah I can see them too. my uncle was a professional Quidditch player and he was one of the best in the league. unfortunately there were wizards who bet a lot of money against his team and they were willing to do anything to not lose the bet. so when my uncle took to the air and the game started, they sent a curse at him and even though it wasn't meant to be deadly, it hit above his heart and it killed him. me and my family were watching the game, it was one of the few times we went to see one of his games. i was ten years old and the game was meant to be a gift for my coming first year at Hogwarts. they caught the scum that were responsible for his death, and from then on, I swore to not commit underhanded crimes and try to live an honorable life. that is why i do not take kindly to people who are very manipulative and hide who they really are. anyway, I'm sorry that you had to experience such a tragedy especially since it was your father who died. my uncle is one of the reason why I really want to get on the Slytherin Quidditch team" he said to Verlin, and gave a sigh. 

he wasn't use to telling people that story but something inside him told him that the girl was someone he could trust and it was good to have someone who shared in his experiences with loss. it would be helpful in case Acacia tried to do something terrible to them.