everybody that can have offspring with us so no goats, no horses, no rabits, and also no apes, pretty easy definition of same specie animal
Only creationists cling to that definition. Evolution killed it dead.
The problem is that change occurs gradually. The common ancestors of you and a cat could certainly interbreed. And so could their offspring, for a long while, until at first you had individuals that were different enough that they couldn't, although most could, and then twogroups that were incompatible, although both could interbreed with a third one, and eventually, all individuals that could interbreed had died off. But what's the exact point where there were two species?
To get the pre-evolution "interbreed" criterion to work, you have to define a proto-species. One individual that is who everyone else is measured against. Otherwise, you wlll run into the problem where your Nth cousin on one side can breed with individuals that you cannot. Where does the line go then?
But by defining a proto-species, you also end up with individuals and groups that will belong to multiple species, because they're midway between the two.
Look at lions and tigers. One variety of tiger can interbreed with lions and create viable offspring, while others cannot. Yet the different types of tigers can interbreed. So our division into species for lions and tigers is not based on breeding.
Your biological parents certainly could breed - there's sad evidence for that. So could their parents. And so on, back through time, back to the common ancestor of you and a chimp. It's a gradual change. Making pigeonholes you can place each individual in is pretty much impossible unless you're prepared to say that your parents were a different species.
We are not good at thinking gradually, alas. We want to classify and group things, to make things simpler. But it's as futile as trying to define where one cloud ends and another one begins. It will always be arbitrary, and subject to change over time.