• Cisco was started by a husband & wife duo - Sandy Lerner and Lenard Bosack
• Steve Jobs did not start Pixar - depending how far you go back, it was Alexander Schure that gave birth to the original roots of the company (as CGL) and later on, branched off by Edwin Catmull and Alvy Ray Smith.
• Elon Musk did not cofound PayPal - He founded X.com and that company merged with Paypal which was founded by Peter Thiel, Max Levchin, Luke Nosek and Ken Howery)
• Same Elon did not cofound Tesla - it was started and incorporated by Martin Eberhard and Marc Tarpenning
• Etsy was not cofounded by Jared Tarbell - It was a trio of Robert Kalin, Chris Macquire and Haim Schoppik that launched the initial company.
I could go on but my memory is escaping me at the moment. I am sure other people have more examples.
tldr; this is common enough. :)