Is he lazy or just developing differently?

[fridayschild]

DS2 is 19 months, has never crawled but just shuffles around on his bum. He will walk for ages holding on to my 2 hands and can manage a couple of steps to me on his own. Lazy or different development?

A paediatrician will tell you that if they're not walking by 18 months, then you may need to get an assessment by a physical therapist/OT, just to rule out that there are no physical problems. Don't think it would hurt to see your GP about your concerns.
On the other hand, if you read any threads about the ages that children have started walking, you will find it varies considerably and some children have been older than 19 months before they started walking.
If I were you I would just set my mind at ease and make an appointment with the doctor. No harm done by it.