The F in "I'm orphan" stands for family.
But there is no F.
The F in "I'm orphan" stands for family.
But there is no F.
Alright listen up buttercup. This joke is saying the letter 'F' in the phrase "I'm orphan" is from the word "family", implying an orphan doesn't have a family. The punchline is that the word orphan doesn't have a letter 'F' so the joke is kinda self-defeating like your attempts at humor.