Nah. It's normal for some cats. I found a pregnant stray once, she had 4 kittens. I kept the youngest and re-homed the others when they were 9-10 weeks old. They were still nursing when they left. The kitten I kept nursed for as long as the mama cat allowed him to. If I recall correctly, he was around 10 months old when she finally cut him off. He was twice her size....it was funny.