Genetics do play a role in how much of a certain type of muscle fibers that someone has, however everyone has untapped strength in some way. You see, when it comes down to strength, it does not always refer to being able to lift massive amounts of weight. Being strong is the ability to perform physically demanding tasks which simply starts from your brain.
Some quick anatomy for you to get my point across. Before you get to the actual muscle fiber, you have three layers of fascia consisting of Epimysium, Perimysium and Endomysium. Inside of that last layer of fascia, you then will find a ton of muscle fibers and inside of those muscle fibers you will find actin and myosin (that is for another blog). Your nerves then run from the brain into the muscle body, stopping at the neuromuscular junction (without going into more detail) allowing for muscle contraction.
Back to the idea of strength, your body will be able to produce force based on the amount of muscle fibers that can contract when required under a specific stimulus. How does this pertain to you? Well, when it comes to programming, everyone will be in a different phase of training. You must go through 2-3 months of proper training in the correct phase, utilizing movements that work well with your body, creating proper stimulus to allow for the body to adapt. Bottom line, if your goal is to get stronger, it all starts from being able to activate more muscle fibers working from the bottom up in the training phase pyramid known as the stabilization phase.