Short answer is yes. Any chest wall anomaly can be associated with any scoliosis as the structures are connected. Not just pectus carinatum, but pectus excavatum as well. They can also occur independently.
Can pectus carinatum cause asthma?
No, asthma is a pulmonary condition. Pectus carinatum is a chest wall deformity. Pectus carinatum is sometimes associated with physical deconditioning.