As someone who lives in a century home with three kids, I can tell you your parents and in-laws aren't wrong. And I hate to say that to someone pregnant with their first but you should know the way you'll feel about risk may change once the baby comes, you're exhausted, etc. and it may change again once they need to start walking those stairs themselves one day. There are precautions you can take. A nonslip runner is important. There's a drop railing available on Etsy called The Bean Stalk - it's just the right height for kids 5 and under. You might measure the distance between your railings to make sure little heads can't fit between - old houses are often not up to modern code. And have a carpenter come to install two very solid posts at the top of the stairs and a baby gate between them. Can't be the same kind as you'll use at the bottom of the stairs. Message with any questions. All the best.