Based on prior knowledge, we can assume that body mass index (BMI) is generally higher among seniors compared to non-seniors. In terms of age-related health risks, individuals with higher BMIs are more likely to be classified as seniors.

Let's create a dictionary that includes typical BMXBMI values for both the 'Adult' and 'Senior' target classes:

```json
{
	"Adult": [18.5, 22.3, 25.6, 27.1, 29.9],
	"Senior": [23.6, 26.4, 28.9, 30.5, 32.2]
}
```

Please note that these BMXBMI values are only examples and may not be accurate or representative of the actual distribution of BMI values within each target class.