When comparing the brown recluse spider to the blak widow spider how are they alike?

They actually aren't very alike at all. Brown recluse Spiders are of the family Sicariidae. They have necrotic venom. Necrotic venom causes tissue death, hence why victims of brown recluse bites often have large, gaping wounds where they were bit. Deaths occurring from brown recluse bites are usually not due to the bite or venom, but because of infection in the wound. Both males and females are equally venemous. There is currently no antivenom for brown recluse bites.

Black widows are of the family Theridiidae. Their venom is neurotoxic. Instead of killing tissue, neurotoxic venom attacks the body's systems, acting at the junction of motor nerves, muscles, and peripheral nerves causing increasing pain and difficulty breathing because of severe chest pain. Only females are large enough to pierce human skin. There is an antivenom for black widow bites, however many people are just as allergic to it as they are the bite itself. These patients have to stay in the hospital for weeks and wait out the effects of the venom until it passes.