Feeling inadequate

My son has never been a good sleeper and once he hit 6 months it has been even worse. He’s struggling to sleep at night and for his naps. The only way I can get him down is on the boob. My mom watches him twice a week and can get him to sleep no problem. Last week I watched my SIL get him to sleep in seconds and it broke my heart. It’s making me feel like a totally inadequate mother because I can’t get my own baby to sleep while others can. Has anyone else been through this?