Given that L1A of subject properties in non-null subject languages emerges later than that of null subject languages, this study aims at determining to what extent the same pattern of acquisition is observed in early child L2A in bilingual immersion settings where English and Spanish are both source and target languages. Using an elicited oral judgment and correction task, L1 English/L2 Spanish and L1 Spanish/L2 English 5-year-olds with the same age of onset, namely 3, are compared in their judgments of purely syntactic subject properties and discourse constraints on subject use. Results suggest that there is developmental asynchrony and that markedness effects might explain why L2 Spanish children generally display significantly more targetlike judgments than the L2 English group.