How to replicate the variable declared in under the struct?

try add UPROPERTY()for your variable,and replicate your struct var like this

//your_struct.h
USTRUCT(BlueprintType)
struct FMyStruct
{
	GENERATED_BODY()
	
	UPROPERTY()
	float my_float=0.0f;

	UPROPERTY()
	int32 my_int=0;
};

//your_character.h
UPROPERTY(Replicated)
FMyStruct mystruct;

public:
	virtual void GetLifetimeReplicatedProps(TArray<class FLifetimeProperty>& OutLifetimeProps) const override;

//your_character.cpp
void AYourCharacter::GetLifetimeReplicatedProps(TArray<class FLifetimeProperty>& OutLifetimeProps) const
{
	Super::GetLifetimeReplicatedProps(OutLifetimeProps);
	DOREPLIFETIME(AYourCharacter,mystruct);
}

(my english is not good:<)