It’s generally frowned on to solicit a hit-person in the fediverse, so as long as you just want some advice, I’m sure anyone—even us, can listen to you and put in our two cents. 😎
I think the person you replied to are a making a joke, suggesting OP wants to solve his problems by hiring a hitman or an assassin. That's the joke. No hate speech involved in the joke. Then to emphasise it's just a joke, and that they don't mean to troll, they actually answer OPs question in a reasonable manner.
If you’d like professional help, https://www.psychologytoday.com/intl/counsellors is a great place. Once you pick a country, you can filter on important characteristics. Many offer virtual appointments and sliding scales. Some offer groups you can join (cheaper and you can benefit from other’s similar experiences).
If you let them know their bullying is getting to you, they'll only continue and increase their torment. You might need to grow a thick skin to get through living with them, but try not to let that harden you to the world too much in the process. They may be physically stronger than you, but that shouldn't stop you from becoming your best self. Not for them; but for yourself.
I am not a therapist or counselor, but know that your worth isn't based on your physical strength, even as a man. You are valuable, and you don't need to be able to overpower people to provide for your partner. If it makes you feel better, I trust "weaker" men more because they tend to be humble and treat me with the respect I deserve. Your siblings sound like they're going to have shallow and unpleasantly interesting lives.